Oxygen concentrators are commonly used to provide enriched oxygen to patients having respiratory problems. Conventional concentrators typically operate on the principles of pressure swing absorption, vacuum swing absorption or vacuum-pressure swing absorption. According to these techniques, air is delivered under pressure to a sieve bed wherein nitrogen and other impurities are absorbed by a filter medium such as zeolite. The trapped air impurities are then purged and vented under reduced pressure or vacuum conditions. In some devices, pressurized air is delivered sequentially to two or more beds in an attempt to improve the efficiency of the system.
Despite advancements in medical concentrator technology, known products are still far from optimally efficient. The compressor used in most such products must generate pressure and air flow that are sufficient to produce an adequate volume of enriched oxygen for the patient. This typically requires the compressor and associated motor to draw a substantial amount of electrical power. Portable concentrators utilize consumable batteries and the significant power demands of such concentrators tend to shorten battery life considerably. In addition, the body of a typical portable concentrator is apt to heat up excessively when operating under the high pressure generated by the compressor. This further reduces the operating efficiency of the apparatus. Moreover, if a compressor operating under high pressure delivers a volume of air to the sieve beds faster than those beds can process the air, the motor driving the concentrator's compressor is apt to stall.
A further disadvantage exhibited by standard concentrators is that the motor is usually controlled to operate at a constant speed (RPM). This tends to produce an inadequate volume of air over the concentrator cycle. If the operating speed is increased to increase air flow, excessive power is consumed and battery life is shortened.